Recent studies have shown that oils containing DAG (DAG oils) can help consumers maintain a healthy weight when being used as part of a healthy diet. Both DAG oils and conventional triacylglycerol-based oils (TAG oils) are absorbed and digested in the same manner but different in how they are metabolized. Resulting from the difference in metabolic pathway, DAG has a lower tendency to be stored as body fat than TAG. These findings have spurred a wide spread interest in development of edible products containing DAG.
DAG oils are suitable to be used as cooking oil and in formulating oil/fat-based products but they are not suitable to be used as frying oil. The presence of DAG in oil during frying facilitates degradation of the oil, thus causing poor flavour in the fried product. Generally, it is desired that frying oil contains not more than 1.5% of DAG.
DAG oils are normally produced according to one of the following methods:                i) esterification of fatty acids with glycerol;        ii) transesterification of oils/fats with glycerol; and        iii) hydrolysis of oils/fats.        
Lipase-catalyzed esterification of fatty acids with glycerol is the preferred method for producing DAG oils. This method is adopted by Kao Corporation for producing its highly successful DAG oil named Enova™ Oil and a description of this method is provided by U.S. Pat. No. 6,326,050.
Short-path distillation is used for processing edible oils whenever any valuable heat sensitive component contained therein, for example tocopherol, tocotrienol, phytosterol and squalene, needs to be distilled or when the oil itself is heat sensitive due to its high unsaturation level. Short-path distillation is also used for removing undesired components such as free fatty acid (FFA), pesticide and cholesterol from edible oils.
In production of DAG oils according to the methods as mentioned above, short-path distillation is normally used for purifying the crude DAG oils produced. Until now, short-path distillation has not been used directly for producing DAG oils.